As technology nodes shrink, in some integrated circuit designs there has been a desire to eliminate use of polysilicon gate electrodes to improve device performance with decreased feature sizes. Replacing polysilicon gate structures with metal gate structures is one solution. Often, metal gate structures utilize aluminum in conjunction with cobalt in their metal fill portion. However, the use of aluminum and cobalt presents several technical challenges in smaller technology nodes. For example, aluminum/cobalt is difficult to recess when forming self-aligned contacts. Further, smaller technology nodes require the use of chemical vapor deposition (CVD) for proper deposition. Often, aluminum deposited by CVD suffers from voids within the metal gate structure. While voiding can occur when depositing a metal into any sized trench, it is particularly troublesome in small trenches. And, as gate lengths decrease the trenches also decrease in size. Depositing metal into the smaller trenches becomes increasingly difficult, and increasingly likely to form voids. Additionally, the use of cobalt in conventional metal gate structures typically causes an increase in resistance.
Accordingly, it is desirable to provide integrated circuits having improved metal gate structures and methods for fabricating integrated circuits having improved metal gate structures. In addition, it is desirable to provide integrated circuits and methods for fabricating integrated circuits which inhibit voiding in the metal gate structures. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.